Turbine engine and particle separators therefore

ABSTRACT

A turbine engine having a bypass fluid conduit coupled to the turbine section includes at least one particle separator located within the bypass fluid conduit to separate particles from a bypass fluid stream prior to the bypass stream reaching the turbine section for cooling. A centrifugal separator for removing particles from a fluid stream includes an angular velocity increaser, a particle outlet, an angular velocity decreaser downstream of the angular velocity increaser, and a bend provided between the angular velocity increaser and the angular velocity decreaser.

BACKGROUND

Turbine engines, and particularly gas or combustion turbine engines, arerotary engines that extract energy from a flow of combusted gasespassing through the engine onto a multitude of turbine blades. Gasturbine engines have been used for land and nautical locomotion andpower generation, but are most commonly used for aeronauticalapplications such as for airplanes, including helicopters. In airplanes,gas turbine engines are used for propulsion of the aircraft.

Gas turbine engines for aircraft are designed to operate at hightemperatures to maximize engine thrust, so cooling of certain enginecomponents, such as the high pressure turbine and the low pressureturbine, may be necessary. Typically, cooling is accomplished by ductingcooler air from the high and/or low pressure compressors to the enginecomponents which require cooling. When cooling the turbines, cooling airmay be passed through an interior of the turbine blades.

Particles, such as dirt, dust, sand, and other environmentalcontaminants, in the cooling air can cause a loss of cooling and reducedoperational time or “time-on-wing” for the aircraft environment. Forexample, particles supplied to the turbine blades can clog, obstruct, orcoat the flow passages and surfaces of the blades, which can reduce thelifespan of the turbine. This problem is exacerbated in certainoperating environments around the globe where turbine engines areexposed to significant amounts of airborne particles.

BRIEF DESCRIPTION

The technology described herein relates to a turbine engine having a fanproviding an ambient air stream through the turbine engine, a compressorsection which receives the ambient air stream and emits a compressedstream, a combustion section which receives the compressed stream andemits a combustion stream which is at a higher temperature than thecompressed stream, a turbine section which receives the combustionstream and emits an exhaust stream which is at a lower temperature thanthe combustion stream, a rotatable drive shaft coupling a portion ofturbine section with a portion of the compression section and defining arotational axis for the turbine engine, a bypass fluid conduit couplingeither the fan or the compressor section to the turbine section whilebypassing at least the combustion section to supply either a portion ofthe ambient air stream or a portion of the compressed stream,respectively, to the turbine section to define a bypass stream, withoutproviding work on the bypass stream that would increase the pressure ordecrease the temperature of the bypass stream, and at least one particleseparator fixedly located in the turbine engine for non-rotationrelative to the rotational axis and further located within the bypassfluid conduit to separate particles from the bypass stream prior to thebypass stream reaching the turbine section to form a reduced-particlestream that is provided to the turbine section for cooling.

In another aspect, the technology described herein relates to acentrifugal separator for removing particles from a fluid stream, thecentrifugal separator including a body having a wall defining a throughpassage, with a separator inlet and a separator outlet, an angularvelocity increaser located within the through passage downstream of theseparator inlet and configured to increase the angular velocity of afluid stream entering the separator inlet as the fluid stream passesthrough the through passage, a particle outlet configured to receive aconcentrated-particle stream containing particles urged toward the wall,an angular velocity decreaser located within the through passage,downstream of the angular velocity increaser and upstream of theseparator outlet, and configured to decrease the angular velocity of areduced-particle stream prior to passing through the separator outlet,and a bend provided in the body between the angular velocity increaserand the angular velocity decreaser.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic cross-sectional diagram of a gas turbine enginefor an aircraft according to a first embodiment;

FIG. 2 is a schematic view showing a bypass cooling circuit for theengine of FIG. 1 according to a second embodiment;

FIG. 3 is a schematic view showing a bypass cooling circuit for theengine of FIG. 1 according to a third embodiment;

FIG. 4 is a cross-sectional view of a centrifugal separator according toa fourth embodiment;

FIG. 5 is a partial perspective view of the centrifugal separator fromFIG. 4, particularly showing an angular velocity increaser in greaterdetail;

FIG. 6 is a partial perspective view of the centrifugal separator fromFIG. 4, particularly showing an angular velocity decreaser in greaterdetail;

FIG. 7 is a partial perspective view of the centrifugal separator fromFIG. 4, particularly showing an outlet passage in greater detail;

FIG. 8 is a view similar to FIG. 4 showing the fluid flow through thecentrifugal separator during operation;

FIG. 9 is a schematic view of the centrifugal separator of FIG. 4,illustrating some other exemplary configurations;

FIG. 10 is a cross-sectional view showing a centrifugal separatoraccording to a fifth embodiment;

FIG. 11 is a cross-sectional view showing a centrifugal separatoraccording to a sixth embodiment;

FIG. 12 is a cross-sectional view showing a centrifugal separatoraccording to a seventh embodiment;

FIG. 13 is a schematic view of a section of the engine from FIG. 1,showing the centrifugal separator of FIG. 4 incorporated with an inducersection of the engine, according to an eighth embodiment;

FIG. 14 is a first perspective view showing an inertial separator forremoving particles from a fluid stream according to a ninth embodiment;

FIG. 15 is a second perspective view showing the inertial separator ofFIG. 14;

FIG. 16 is a top view of the inertial separator from FIG. 14;

FIG. 17 is a bottom view of the inertial separator from FIG. 14;

FIG. 18 is a schematic view of a section of the engine from FIG. 1,showing the inertial separator of FIG. 14 incorporated with an inducersection of the engine, according to a tenth embodiment;

FIG. 19 is a schematic view showing a modified version of an inertialseparator according to an eleventh embodiment;

FIG. 20 is a perspective view showing a centrifugal separator forremoving particles from a fluid stream according to a twelfthembodiment;

FIG. 21 is a cross-sectional view of the centrifugal separator from FIG.20;

FIG. 22 is a view similar to FIG. 21 showing the fluid flow through thecentrifugal separator during operation.

FIG. 23 is a schematic view of a section of the engine from FIG. 1,showing the centrifugal separator of FIG. 20 incorporated with aninducer section of the engine, according to a thirteenth embodiment;

FIG. 24 is a perspective view showing an inducer section that can beincorporated in the engine of FIG. 1 according to a fourteenthembodiment;

FIG. 25 is a close-up view of a portion of the inducer section of FIG.24, showing the fluid flow through the inducer section during operation;

FIG. 26 is a schematic view of a section of the engine from FIG. 1,showing a portion of the bypass cooling circuit incorporated with the HPturbine according to a fifteenth embodiment;

FIG. 27 is a schematic view of a section of the engine from FIG. 1showing a shroud assembly according to a sixteenth embodiment;

FIG. 28 is a schematic view of a section of the engine from FIG. 1showing a shroud assembly according to a seventeenth embodiment;

FIG. 29 is a schematic view of a section of the engine from FIG. 1showing a shroud assembly according to an eighteenth embodiment;

FIG. 30 is a schematic view of a section of the engine from FIG. 1,showing a baffle-type separator according to a nineteenth embodiment;

FIG. 31 is a schematic view of a section of the engine from FIG. 1,showing a baffle-type separator according to a twentieth embodiment; and

FIG. 32 is a schematic view of a section of the engine from FIG. 1,showing a baffle-type separator according to a twenty-first embodiment.

DETAILED DESCRIPTION

The embodiments of the technology described herein are directed tosystems, methods, and other devices related to particle separation,particularly in a turbine engine, and more particularly to particleseparation for the removal of particles from a cooling air flow in aturbine engine. For purposes of illustration, the technology will bedescribed with respect to an aircraft gas turbine engine. It will beunderstood, however, that the technology is not so limited and may havegeneral applicability in non-aircraft applications, such as other mobileapplications and non-mobile industrial, commercial, and residentialapplications.

FIG. 1 is a schematic cross-sectional diagram of a gas turbine engine 10for an aircraft. The engine 10 has a generally longitudinally extendingaxis or centerline 12 extending forward 14 to aft 16. The engine 10includes, in downstream serial flow relationship, a fan section 18including a fan 20, a compressor section 22 including a booster or lowpressure (LP) compressor 24 and a high pressure (HP) compressor 26, acombustion section 28 including a combustor 30, a turbine section 32including a HP turbine 34, and a LP turbine 36, and an exhaust section38.

The fan section 18 including a fan casing 40 surrounding the fan 20. Thefan 20 includes a plurality of fan blades 42 disposed radially about thecenterline 12.

The HP compressor 26, the combustor 30, and the HP turbine 34 form acore 44 of the engine 10 which generates combustion gases. The core 44is surrounded by core casing 46 which can be coupled with the fan casing40.

A HP shaft or spool 48 disposed coaxially about the centerline 12 of theengine 10 drivingly connects the HP turbine 34 to the HP compressor 26and a LP shaft or spool 50, which is disposed coaxially about thecenterline 12 of the engine 10 within the larger diameter annular HPspool 48, drivingly connects the LP turbine 36 to the LP compressor 24and fan 20.

The LP compressor 24 and the HP compressor 26 respectively include aplurality of compressor stages 52, 54, in which a set of compressorblades 56, 58 rotate relative to a corresponding set of staticcompressor vanes 60, 62 (also called a nozzle) to compress or pressurizethe stream of fluid passing through the stage. In a single compressorstage 52, 54, multiple compressor blades 56, 58 may be provided in aring and may extend radially outwardly relative to the centerline 12,from a blade platform to a blade tip, while the corresponding staticcompressor vanes 60, 62 are positioned downstream of and adjacent to therotating blades 56, 58.

In one example, the LP compressor 24 may include 4 stages and the HPcompressor 26 may include 10 stages, although the number of compressorstages varies in different types of engines. It is noted that the numberof blades, vanes, and compressor stages shown in FIG. 1 were selectedfor illustrative purposes only, and that other numbers are possible.

The HP turbine 34 and the LP turbine 36 respectively include a pluralityof turbine stages 64, 66, in which a set of turbine blades 68, 70 arerotated relative to a corresponding set of static turbine vanes 72, 74(also called a nozzle) to extract energy from the stream of fluidpassing through the stage. In a single turbine stage 64, 66, multipleturbine blades 68, 70 may be provided in a ring and may extend radiallyoutwardly relative to the centerline 12, from a blade platform to ablade tip, while the corresponding static turbine vanes 72, 74 arepositioned upstream of and adjacent to the rotating blades 68, 70.

In one example, the HP turbine 34 may include 2 stages and the LPturbine 36 may include 6 stages, although the number of turbine stagesvaries in different types of engines. It is noted that the number ofblades, vanes, and turbine stages shown in FIG. 1 were selected forillustrative purposes only, and that other numbers are possible.

In operation, the rotating fan 20 supplies ambient air to the LPcompressor 24, which then supplies pressurized ambient air to the HPcompressor 26, which further pressurizes the ambient air. Thepressurized air from the HP compressor 26 is mixed with fuel incombustor 30 and ignited, thereby generating combustion gases. Some workis extracted from these gases by the HP turbine 34, which drives the HPcompressor 26. The combustion gases are discharged into the LP turbine36, which extracts additional work to drive the LP compressor 24, andthe exhaust gas is ultimately discharged from the engine 10 via theexhaust section 38. The driving of the LP turbine 36 drives the LP spool50 to rotate the fan 20 and the LP compressor 24.

Some of the ambient air supplied by the fan 20 may bypass the enginecore 44 and be used for cooling of portions, especially hot portions, ofthe engine 10, and/or used to cool or power other aspects of theaircraft. This air is often referred to as bypass air, which is one formof a cooling fluid when used to cool. In the context of a turbineengine, the hot portions of the engine are normally downstream of thecombustor 30, especially the turbine section 32, with the HP turbine 34being the hottest portion as it is directly downstream of the combustorsection 28. Other portions of the aircraft, not part of the engine, maybe considered a hot portion that is to be cooled.

FIG. 2 is a schematic view showing a portion of the engine 10 fromFIG. 1. The engine 10 can further include a bypass cooling circuit 76for providing cooling fluid to at least one hot portion 78 of the engine10 during operation. In order to cool the hot portion 78 of the engine,the cooling fluid is at a temperature that is less than the operationaltemperature of the hot portion 78; i.e. the temperature of the hotportion 78 during normal operation of the engine 10. As indicated inFIG. 2, the hot portion 78 of the engine 10 may include, but is notlimited to, the HP turbine 34 and the walls of the combustor 30. Asource of cooling fluid 80 entering the bypass cooling circuit 76 maybe, but is not limited to, fluid discharged from the fan 20, the LPcompressor 24, or the HP compressor 26.

The bypass cooling circuit 76 includes a bypass conduit 82 whichbypasses at least a portion of the core 44 of the engine 10 in order toprovide cooling fluid to the hot portion 78 of the engine 10. Air mayenter the bypass conduit 78 from the source of cooling fluid 80, and mayexit the bypass conduit 82 at the hot portion 78 of the engine 10 towhich the cooling fluid is to be supplied.

In one configuration, the bypass cooling circuit 76 can include a flowdivider 84 which separates the fluid stream from the source of coolingfluid 80 into a core fluid stream which enters the core 44 and a bypassfluid stream which enters the bypass conduit 82. In one configuration,the flow divider 84 can be located between fan blades 42 and the LPcompressor 24 (FIG. 1), with the core fluid stream entering the LPcompressor 24 and the surrounding bypass fluid stream entering thebypass conduit 78. However, the location of the flow divider 84 can varydepending on the source of cooling fluid 80.

The bypass cooling circuit 76 may include a particle separator 86 forseparating particles, which may include, but is not limited to, dirt,dust, debris, and other contaminants, from the cooling fluid stream fromthe source prior to being supplied to the hot portion of the engine 10.The particle separator 86 may, for example, be an inertial separatorwhich separates particles from the cooling air flow using a combinationof forces, such as centrifugal, gravitational, and inertial. Morespecifically, the inertial separator may be a centrifugal or cyclonicseparator, which uses cyclonic action to separate particles from thecooling air flow.

The particle separator 86 may define a portion of the bypass conduit 78,and may be located anywhere along the bypass conduit 78. The particleseparator 86 includes a separator inlet 88, a separator outlet 90, and aparticle outlet 92. The cooling fluid stream entering the particleseparator 86 at the separator inlet 88 is separated into aconcentrated-particle stream which contains at least some of theparticles from the cooling fluid stream, and a reduced-particle streamwhich contains fewer or a lower concentration of particles than theconcentrated-particle stream. The reduced-particle stream exits theparticle separator 86 via the separator outlet 90, and is provided tothe hot portion 78 of the engine 10 for cooling. Theconcentrated-particle stream exits the particle separator 86 via theparticle outlet 92, and may be exhausted from the engine 10 or may beutilized in other portion of the engine 10. For example, theconcentrated-particle stream may be used for driving the LP turbine 36,dumped from the engine 10 under the fan casing 40, or used for someauxiliary function 94, some examples of which are described in detailbelow. Alternatively, the particle outlet 92 may be coupled with aparticle collector to collect the separated particles for laterdisposal.

In one example, the particle separator 86 can include at least aparticle concentrator 96 and a flow splitter 98. The particleconcentrator 96 is a structure that concentrates the particles containedin the fluid stream in one portion of the fluid stream. The flowsplitter 98 is a structure that splits a fluid stream into separatestreams. In this example, the particle concentrator 96 is fluidlydownstream of the separator inlet 88, and generally moves the particlescontained within the entire the cooling fluid stream in one portion ofthe cooling fluid stream to thereby create the concentrated-particlestream, with the remaining fluid now having fewer particles (though someparticles may still be present) to form the reduced-particle stream. Theflow splitter 98 is fluidly downstream of the particle concentrator 96,and splits the concentrated-particle stream from the reduced-particlestream. These two streams can be directed to different areas of theengine 10, with the reduced-particle stream exiting the particleseparator 86 via the separator outlet 90 and the reduced-particle streamfrom the exiting via the particle outlet 92.

It is noted that while only one particle separator 86 is shown in FIG.2, the bypass cooling circuit 76 may include multiple particleseparators. The multiple particle separators may be arranged inparallel, such that the cooling fluid stream is divided to pass throughone of the multiple particle separators, or may be arranged in series,such that the cooling fluid stream sequentially passes through multipleparticle separators for the separation of increasingly smaller or finerparticles at each separation stage.

Optionally, the concentrated-particle stream exiting the particleseparator 86 may be passed through a heat exchanger 100 to cool theconcentrated-particle stream and/or a filter 102 to remove at least someof the particles from the concentrated-particle stream, prior to beingexhausted from the engine 10 or utilized in other portion of the engine10. The filter 102 can be a line replaceable unit, and may particularlybe useful if the concentrated-particle stream is to be reintroduced intothe hot fluid path of the engine 10. Some non-limiting examples of asuitable filter 102 includes a ceramic filter or metallic foam filter.

As yet another option, the bypass cooling circuit 76 can include a valve104 selectively directing the bypass cooling air to the particleseparator 86, or directly to the hot portion 78 of the engine 10. Thevalve 104 is located within the bypass conduit 78, such that the bypasscooling air may be passed directly to the hot portion 78 while stillbypassing the core 44, as well as bypassing the particle separator 86.The valve 104 may be used to turn off flow to the particle separatorwhen particle separation is not required, such as at cruise altitudes.

FIG. 3 shows one specific configuration of the bypass cooling circuit 76in which the reduced-particle stream can be provided to the HP turbine34, according to a third embodiment. The bypass cooling circuit 76 canfurther include an inducer section 106 for injecting thereduced-particle stream into the HP turbine 34. In a typical engine 10,the inducer section 106 accelerates the cooling fluid stream and alsoturns the cooling fluid stream from a substantially axial directionparallel to the centerline 12 of the engine 10 to a direction generallytangential to the face of the blades 68, so as to tangentially injectthe cooling fluid stream into the rotating blades 68 at a rotational ortangential speed and direction substantially equal to that of the blades68. By “generally tangential”, the cooling fluid stream may be orientedat a slightly shallow angle with respect to a true tangential direction.

In the present embodiment, the inducer section 106 can form a portion ofthe bypass conduit 82, and can include at least one inducer 108. Theinducer section 106 can include multiple inducers 108 disposed in acircumferential array about the centerline 12 of the engine 100. Eachinducer 108 can have at least one associated particle separator 86, suchthat each inducer 108 receives the reduced-particle flow from theassociated particle separator 86.

The inducer 108 receives the reduced-particle stream from the particleseparator 86 and accelerates and/or turns the reduced-particle stream soas to inject the reduced-particle stream into the rotating blades 68 ofthe HP turbine 34 at a velocity and direction substantially equal tothat of the rotating blades 68. Fluid leaving the inducer 108 isoriented in a direction generally tangential to the face of the blades68.

Optionally, the particle separator 86 can be configured to perform theacceleration function, while the inducer 108 may perform the turningfunction, with or without further acceleration of the fluid stream. Theparticle separator 86 can provide a fluid stream to the inducer section106, or may be included within the inducer section 106 itself.

FIGS. 4-25 show various embodiments of particle separators which may beincorporated into the engine 10 shown in FIG. 1, the bypass coolingcircuit 76 shown in FIGS. 2-3, or an inducer section of the engine 10.It is understood that the engine 10 or bypass cooling circuit 76 mayincorporate more than one of the following particle separators.Furthermore, the engine 10 or bypass cooling circuit 76 may incorporatea combination of the following particle separators.

FIG. 4 is a cross-sectional view showing a centrifugal separator 110 forremoving particles from a fluid stream according to a fourth embodiment.The centrifugal separator 110 includes a body 112 having a wall 114defining a through passage 116, with a separator inlet 118 whichreceives a fluid stream, a separator outlet 120 through which areduced-particle stream is passed, and a particle outlet 122 throughwhich a concentrated-particle stream is passed. The through passage 116defines a centerline 124 of the centrifugal separator 110, with thecenterline 124 generally defining an upstream direction 126 anddownstream direction 128 with respect to the centrifugal separator 110.

The centrifugal separator 110 further includes a particle concentrator130 and a flow splitter 132. The particle concentrator 130 of theillustrated embodiment includes an angular velocity increaser 134provided within the through passage 116, downstream of the separatorinlet 118, which is configured to impart an increased angular velocityto the incoming fluid stream. An angular velocity decreaser 136 is alsoprovided within the through passage 116, downstream of the angularvelocity increaser 134 and upstream of the separator outlet 120, and isconfigured to impart a decreased angular velocity to thereduced-particle stream exiting through the separator outlet 120.

A bend 138 is provided in the body 112 between the angular velocityincreaser 134 and the angular velocity decreaser 136. Upstream anddownstream of the bend 138, the body 112 is substantially straight orlinear. The bend 138 functions as an inertial separator in combinationwith the centrifugal separation provided by the angular velocityincreaser 134. The centerline 124 follows the bend 138, which in theillustrated embodiment defines a bend angle of approximately 45 degreesbetween the portions of the centerline 124 upstream and downstream ofthe bend 138. The separator inlet 118 and the separator outlet 120 shownherein are axially-centered on the centerline 124, but are non-axialwith each other, such that the separator inlet 118 and the separatoroutlet 120 lie in non-parallel planes.

In this embodiment, the body 112 can define an outer body, with the wall114 provided as an outer, annular wall. A center body 140 can beprovided within the through passage 116, spaced from the annular wall114, and can extend axially along the centerline 124 of the centrifugalseparator 110. The center body 140 services to reduce pressure loss atthe center region of the through passage 116.

In the illustrated embodiment, the center body 140 can extendcontinuously between, and beyond, the angular velocity increaser 134 andthe angular velocity decreaser 136. The center body 140 includes a firstterminal end 142 facing the separator inlet 118 and a second terminalend 144 facing the separator outlet 120, which are joined by acylindrical core 146. The first terminal end 142 can be rounded toretard flow separation, while the second terminal end 144 can be taperedto reduce the cross-sectional area of the center body 140, whichaccelerates the fluid stream. The first terminal end 142 joins the core146 at a first tapered portion 148 at which the angular velocityincreaser 134 is located. The core 146 joins with the second terminalend 144 at a second tapered portion 150 at which the angular velocitydecreaser 136 is located. The angular velocity increaser 134 and theangular velocity decreaser 136 can be spaced from each other to define aseparation chamber 152 therebetween forming a portion of the throughpassage 116 between the core 146 and the annular wall 114.

The flow splitter 132 is fluidly downstream of the particle concentrator130, and splits the concentrated-particle stream from thereduced-particle stream. The flow splitter 132 of the illustratedembodiment includes an inner annular wall 154 spaced radially inwardlyfrom the outer annular wall 114, which defines, at least in part, theparticle outlet 122.

The particle outlet 122 includes at least one outlet passage 156 havingat least one inlet opening 158 and at least one outlet opening 160. Asshown, one annular outlet passage 156 is defined between the outerannular wall 114 and the inner annular wall 154, with a circumferentialinlet opening 158 defined at an upstream edge 162 of the inner annularwall 154. The outlet passage 156 shown herein has an axially-increasingcross-section, such that the cross-section of outlet passage 156 at theinlet opening 158 is smaller than the cross-section of outlet passage156 downstream of the inlet opening 158. In another configuration, theoutlet passage 156 can have an axially-constant cross-section.

As shown, the outlet passage 156 includes one outlet opening 160 definedby an outlet conduit 164 projecting from the outer annular wall 114 ofthe centrifugal separator 110. The downstream end of the outlet passage156 can be closed by an end wall 166 joining the outer and inner annularwalls 114, 154, such that the fluid stream is directed through theoutlet conduit 164, which is shown as being provided on the outerannular wall 114 upstream of the end wall 166. In other configurations,the outlet opening 160 could be provided in the end wall 166, itself.

The angular velocity decreaser 136 is located downstream of the inletopening 158 to the outlet passage 156, with the inner annular wall 154extending past the angular velocity decreaser 136. A portion of theinner annular wall 154 downstream of the angular velocity decreaser 136can extend beyond the end wall 166 to define the separator outlet 120.

Alternatively, the outlet passage 156 can be provided with multipleinlet openings 158 adjacent the outer annular wall 114. In yet anotheralternatively, multiple outlet passages 156 can be provided, andradially spaced about the outer annular wall 114. The multiple outletpassages 156 can each have an inlet opening 158, with the inlet openings158 being intermittent and spaced about the circumference of the body112. Likewise, the outlet passage 156 can be provided with multipleoutlet openings 160.

In one exemplary configuration, the outer annular wall 114 can define adiameter D. The inlet opening 158 of the outlet passage 156 can belocated 1-20 D downstream of the angular velocity increaser 134, wherethe diameter D corresponds to the diameter D of the outer annular wall114 at the inlet opening 158. Furthermore, the inlet opening 158 candefine a radial segment R of 1-10% of the diameter D at the inletopening 158. Still further, the outlet passage 156 can extend radiallyinwardly into the through passage 1-20% of the diameter D in thedownstream direction 128. It is noted that the diameter D of the outerannular wall 114 can, as shown, be substantially continuous along atleast the separation chamber 152, but it is possible for the diametervary.

FIG. 5 is a partial perspective view of the centrifugal separator 110from FIG. 4, showing the angular velocity increaser 134 in greaterdetail. The angular velocity increaser 134 can include a plurality ofswirl vanes 168 provided in the though passage 116 for imparting aswirling motion to the fluid stream. The swirl vanes 168 can becircumferentially spaced evenly about the centerline 124 of the throughpassage 116. The swirl vanes 168 can further be fixed in position withinthe through passage 116, such that they remain stationary as fluidpasses the swirl vanes 168. Other structures, such as a screw-type vane,may be used.

As illustrated, each swirl vane 168 can comprise an airfoil-shaped body170 with a rounded leading edge 172 followed by a tapered trailing edge174 which is downstream of the leading edge 172. The airfoil-shapedbodies 170 are cambered such that the leading edges 172 deflect theincoming fluid stream in a swirling flow, thereby generating a vortex orswirling flow about the center body within the separation chamber 152.The trailing edges 174 are oriented in generally the same direction inwhich it is desired to swirl the fluid stream.

The swirl vanes 168 can extend radially from the center body 140 to theannular wall 114. More particularly, the rounded leading edges 172 canbe located slightly downstream of the first terminal end 142 of thecenter body 140, with the airfoil-shaped bodies 170 being located on thefirst tapered portion 148.

FIG. 6 is a partial perspective view of the centrifugal separator 110from FIG. 4, showing the angular velocity decreaser 136 in greaterdetail. The angular velocity decreaser 134 can include a plurality ofdeswirl vanes 174 provided in the though passage 116 for straighteningthe fluid stream and substantially reducing or removing any swirl fromthe reduced-particle stream. The deswirl vanes 174 can becircumferentially spaced evenly about the centerline 124 of the throughpassage 116. The deswirl vanes 174 can further be fixed in positionwithin the through passage 116, such that they remain stationary asfluid passes the deswirl vanes 174.

As illustrated, each deswirl vane 174 can comprise an airfoil-shapedbody 176 with a leading edge 178 followed by a trailing edge 180 whichis downstream of the leading edge 178. The airfoil-shaped bodies 176 arecambered such that the leading edges 178 are directed in generally thesame direction as the swirling air flow entering the angular velocitydecreaser 136 from the separation chamber 152, while the trailing edges180 are directed substantially in the direction in which it is desiredfor the flow to exit the vanes 174, i.e., with little or no swirlcomponent of velocity.

The deswirl vanes 174 can extend radially from the center body 140 tothe inner annular wall 154. More particularly, the trailing edge 180 canbe located slightly upstream of the second terminal end 144 of thecenter body 140, with the airfoil-shaped bodies 176 being located on thesecond tapered portion 150.

FIG. 7 is a partial perspective view of the centrifugal separator 110from FIG. 4, showing the outlet passage 156 in greater detail. Theoutlet passage 156 can include a plurality of vanes 182 for deswirlingthe flow. The vanes 182 can be circumferentially spaced evenly about thecenterline 124 within the outlet passage 156, and can further be fixedin position within the outlet passage 156, such that the vanes 182remain stationary as the concentrated-particle stream passes the vanes182. The vanes 182 can extend radially from the inner annular wall 154to the outer annular wall 114, and are upstream of the outlet conduit164.

As illustrated, each vane 182 can comprise a cambered body 184 with aleading edge 186 followed by a trailing edge 188 which is downstream ofthe leading edge 186. The cambered bodies 184 are oriented such that theflow entering the outlet opening 158 is deswirled and define separateinlet paths 190 through the outlet passage 156 between adjacent vanes182.

FIG. 8 is a view similar to FIG. 4 showing the fluid flow through thecentrifugal separator 110. In operation, a fluid stream enters theseparator inlet 118 in a substantially axial direction with respect tothe centerline 124, and the swirl vanes 168 impart a swirling flow tothe incoming fluid stream, thereby generating a vortex within theseparation chamber 152. Due to their greater inertia, particles withinthe vortex are forced radially outwardly toward the outer wall 114. Theflow splitter 132 splits a radially-outward portion of the fluid streamalong with entrained particles within the radially-outward portion froma radially-inward portion of the fluid stream to form aconcentrated-particle stream and a reduced-particle stream. Thereduced-particle stream passes within the inner annular wall 154 andthrough the separator outlet 120. The concentrated-particle streamleaves the separator 110 by passing outside the inner annular wall 154and through the outlet opening 160. It is noted that for purposes ofsimplification, the streamlines for the concentrated-particle stream arenot shown in FIG. 8.

The angular velocity increaser 134 and the angular velocity decreaser136 can be configured to respectively increase and decrease the angularvelocity of the fluid stream by substantially opposite amounts. Inparticular, the swirl vanes 168 are oriented relative to the fluidstream, which generally enters the separator inlet 118 in an axialdirection following the centerline 124, to increase the angular velocityof the fluid stream as the fluid stream passes through the swirl vanes168. Correspondingly, the deswirl vanes 174 are oriented relative to thefluid stream, which generally approaches the angular velocity decreaser136 in a swirling motion around the centerline 124, to decrease theangular velocity of the reduced-particle fluid stream by substantiallythe same amount as the swirl vanes 168 increased the angular velocity174.

FIG. 9 is a schematic view of the centrifugal separator 110 of FIG. 4,illustrating some other exemplary configurations of the bend 138.Upstream and downstream of the bend 138, the body 112 is substantiallystraight or linear. The centerline 124 follows the bend 138, which inthe illustrated embodiment defines bend angle A between the portions ofthe centerline 124 upstream and downstream of the bend 138. Thecentrifugal separator 110 can, for example, be configured to have a bend138 with bend angle A ranging from greater than zero but less than orequal to 90 degrees. It is noted that the angle A can by in plane andout of plane and form a compound angle in three dimensions.

Furthermore, the centrifugal separator 110 can be provided with acontinuous center body 140, similar to what is shown in FIG. 4 in whichthe center body 140 extends continuously between the angular velocityincreaser 134 and the angular velocity decreaser 136, or canalternatively be provided with a non-continuous center body, in whichthe center body 140 has at least one discontinuously between the angularvelocity increaser 134 and the angular velocity decreaser 136; someexamples of this are shown in the following figures.

FIG. 10 is a cross-sectional view showing a modified version of acentrifugal separator 110′ according to a fifth embodiment, in whichelements in common with the centrifugal separator 110 of FIG. 4 arereferred to by the same reference numerals bearing a prime (′) symbol.The centrifugal separator 110′ differs from the centrifugal separator110 of FIG. 4 by including a non-continuous center body 192, which istypically easier to manufacture and assemble, along with weighing lessand having lower costs. The non-continuous center body 192 can beprovided within the through passage 116′, spaced from the annular wall114′, and can extend axially along the centerline 124′ of thecentrifugal separator 110′. In the illustrated embodiment, the centerbody 192 extends non-continuously between, and beyond, the angularvelocity increaser 134′ and the angular velocity decreaser 136′.

The non-continuous center body 192 includes leading body 194 and atrailing body 196 which is downstream of and separate from the leadingbody 194. The leading body 194 includes a first terminal end 198 facingthe separator inlet 118′ and a second terminal end 200 facing theseparation chamber 152′, which joins the first terminal end 198 at atapered portion 202 at which the angular velocity increaser 134′ islocated. The first terminal end 198 can be tapered, while the secondterminal end 200 can be rounded or tapered. The trailing body 196includes a first terminal end 204 facing the separation chamber 152′ anda second terminal end 206 facing the separator outlet 120′, which joinsthe first terminal end 204 at a tapered portion 208 at which the angularvelocity decreaser 136′ is located. The first terminal end 204 can berounded or tapered, while the second terminal end 206 can be tapered.

FIG. 11 is a cross-sectional view showing yet another modified versionof a centrifugal separator 110″ according to a sixth embodiment, inwhich elements in common with the centrifugal separator 110′ of FIG. 10are referred to by the same reference numerals bearing a double prime(″) symbol. The centrifugal separator 110″ differs from the centrifugalseparator 110′ of FIG. 10 by including a bend 138″ of substantially 90degrees, which provides for greater inertial separation as well asimproving ease of installation in some environments.

FIG. 12 is a cross-sectional view showing yet another modified versionof a centrifugal separator 210 according to a seventh embodiment. Thecentrifugal separator 210 differs from the centrifugal separators 110,110′, 110″ of FIGS. 4-11 by the elimination of any bend between anangular velocity increaser 212 and an angular velocity decreaser 214 ofthe separator 210.

The centrifugal separator 210 includes a body 216 having a wall 218defining a through passage 220, with a separator inlet 222 whichreceives a fluid stream, a separator outlet 224 through which areduced-particle stream is passed, and a particle outlet 226 throughwhich a concentrated-particle stream is passed. The through passage 220defines a centerline 228 of the centrifugal separator 210, with thecenterline 228 generally defining an upstream direction 230 anddownstream direction 232 with respect to the centrifugal separator 210.The centrifugal separator 210 shown in FIG. 12 is an axial-flowseparator, with the separator inlet 222 and separator outlet 224co-axially aligned and lying along the centerline 228 defined by thethrough passage 220. The centrifugal separator 210 further includes aparticle concentrator 234, which includes the angular velocity increaser212, and a flow splitter 236.

In this embodiment, the body 216 can define an outer body, with the wall218 provided as an outer, annular wall. A center body 238 can beprovided within the through passage 220, spaced from the outer annularwall 218, and can extend axially along the centerline 228. The angularvelocity increaser 212 and angular velocity decreaser 214 are located onthe center body 238. Further, the angular velocity increaser 212,angular velocity decreaser 214, and center body 238 can be configuredsubstantiantially as described above for the angular velocity increaser134, angular velocity decreaser 136, and center body 140 of FIG. 4.

The flow splitter 236 is fluidly downstream of the particle concentrator234, and splits the concentrated-particle stream from thereduced-particle stream. The flow splitter 236 of the illustratedembodiment includes an inner annular wall 240 spaced radially inwardlyfrom and formed integrally with, the outer annular wall 218, whichdefines, at least in part, the particle outlet 226.

The particle outlet 226 includes at least one outlet passage 242 havingat least one inlet opening 244 and at least one outlet opening 246. Asshown, one annular outlet passage 242 is defined, with a circumferentialinlet opening 244 defined at an upstream edge 248 of the inner annularwall 240 and one outlet opening 246 defined in the outer annular wall218 and extending in a radial direction. The outlet passage 242 shownherein has an axially-increasing cross-section, such that thecross-section of outlet passage 242 at the inlet opening 244 is smallerthan the cross-section of outlet passage 242 downstream of the inletopening 244. In another configuration, the outlet passage 242 can havean axially-constant cross-section. Also as shown, the outlet passage 242is free from any vanes, although vanes 182 similar to those shown inFIG. 7 could also be incorporated in this embodiment.

FIG. 13 is a schematic view of a section of the engine 10, showing thecentrifugal separator 110 of FIG. 4 incorporated with the inducersection 106, according to an eighth embodiment. As described above, withreference to FIG. 3, the inducer section 106 can form a portion of thebypass conduit 82 of the bypass cooling circuit 76, and can include atleast one inducer 108. The inducer 108 includes an inducer inlet 302 andan inducer outlet 304. The separator outlet 120 of the centrifugalseparator 110 can be located upstream of the inducer 108 and can be influid communication with the inducer inlet 302, such that the fluidstream supplied to the inducer 108 is a reduced-particle stream. Theinducer 108 accelerates and/or turns the reduced-particle stream andinjects the reduced-particle stream into the HP turbine 34.

The concentrated-particle stream from the centrifugal separator 110 isnot directed to the inducer 108 or HP turbine 34, but rather is passedfrom the particle outlet 122 through an extraction vent 306.Alternatively, the concentrated-particle stream may be directed towardthe rotor wheel space in the HP turbine. The extraction vent 306 canlead to the LP turbine 36, an exhaust for the engine 10 under the fancasing 40, or to another portion of the engine 10 to be used for someauxiliary function 94, as indicated schematically in FIG. 3.

FIGS. 14-15 are perspective views showing an inertial separator 250 forremoving particles from a fluid stream according to a ninth embodiment.The inertial separator 250 includes a body 252 having a wall 254defining a through passage 256, with at least one separator inlet 258which receives a fluid stream, at least one separator outlet 260 throughwhich a reduced-particle stream is passed, and at least one particleoutlet 262 through which a concentrated-particle stream is passed. Thethrough passage 256 defines a centerline 264 of the inertial separator250, with the centerline 264 generally defining an upstream direction266 and downstream direction 268 for fluid flow. In FIGS. 14-15, aportion of the wall 254 is cut-away to better show the through passage256.

The inertial separator 250 further includes a particle concentrator 270and a flow splitter 272 fluidly downstream of the particle concentrator270. The particle concentrator 270 of the illustrated embodimentincludes at least one turn 274 provided in the body 252 between the atleast one separator inlet 258 and the at least one separator outlet 260.The at least one turn 274 defines an inside 276 and outside 278 for thethrough passage 256. The at least one turn 274 forces the fluid streampassing through the through passage 256 to change direction, and theinertia of at least some of the particles within the fluid stream causesthe particles to move toward the outside 278 of the through passage 256.The flow splitter 272 splits the radially-outward portion of the fluidstream, i.e. the portion of the fluid stream closer to the outside 278,from the radially-inward portion of the fluid stream, i.e. the portionof the fluid stream closer to the inside 276, to form theconcentrated-particle stream, which is passed through the particleoutlet 262, and the reduced-particle stream, which is passed through theseparator outlet 260.

In this embodiment, the wall 254 of the body 252 can be a tubular walldefining a conduit having a substantially rectilinear cross-sectionalshape. Other cross-sectional shapes are also possible, such as annular.The tubular wall 254 is substantially hollow or free from obstructions,such that a fluid stream entering the inertial separator 250 flowsaxially along the centerline 264, until reaching the flow splitter 272.

An inlet portion 282 of the tubular wall 254 defines the separator inlet258, and an outlet portion 284 of the tubular wall 254 defines theseparator outlet 260. The inlet and outlet portions 282, 284 can besubstantially straight, with the centerline 264 of the through passage256 at the inlet and outlet portions 282, 284 being substantiallylinear.

The at least one turn 274 can be defined with respect to a turn axis286, such that the centerline 264 of the through passage 256 winds aboutthe turn axis 286 at the one turn 274. The body 252 can thereforeinclude at least one winding portion 288 of the tubular wall 254 todefine the at least one turn 274. At the winding portion 288, thecenterline 264 can follow various forms of curves. For example, thecenterline 264 at the winding portion 288 can follow a plane curve or aspace curve. In another example, the radius of the at least one turn274, defined as the distance between the centerline 264 and the turnaxis 286 can be constant or changing along the winding portion 288,including increasing or decreasing in the downstream direction 268. Inyet another example, the pitch of the at least one turn 274, defined asthe angle between the centerline 264 and the turn axis 286 at a givenpoint along the centerline 264, can be constant or changing along thewinding portion 288, including increasing or decreasing in thedownstream direction 268. Some non-limiting examples of shapes for thewinding portion 288 in which the centerline 264 follows a space curveinclude corkscrew, helical and spiral.

The at least one turn 274 can further be configured to effect differingdegrees of direction change in the fluid stream. In one example, the atleast one turn 274 effects at least a 45 degree change of direction ofthe fluid stream; more preferably, the at least one turn effects atleast a 180 degree change of direction of the fluid stream, still morepreferably, the at least one turn effects at least a 360 degree changeof direction of the fluid stream.

The at least one turn 274 can further be configured to impart a Stokesnumber to the fluid stream which will force at least some of theparticles entrained in the fluid stream to move to the outside of thethrough passage. In one example, the at least one turn 274 can furtherbe configured to impart a Stokes number of 0.01 to 20 to the fluidstream.

The particle concentrator 270 of the inertial separator 250 can furtherinclude multiple, discrete turns, as shown in FIG. 15. The particleconcentrator 270 in particular includes a leading turn 274L which isdownstream of the inlet portion 282 and a trailing turn 274T which isdownstream of the leading turn 274L. In the illustrated embodiment, thefirst turn 274L effects at least a 360 degree change in the direction ofthe fluid stream entering the inertial separator 250 at the separatorinlet 258, while the second turn 274T effects at least a 90 degreechange in the direction of the fluid stream. The conduit 282 cantherefore include a leading winding portion 288L defining the leadingturn 274L and a trailing winding portion 288T defining the trailing turn274T, both of which wind about the turn axis 286.

The portion of the tubular wall 254 forming the particle concentrator270 can further have a constant or changing cross-sectional area. In theillustrated embodiment, a first transition portion 290 defines adecreasing cross-sectional area of the tubular wall 254 leading into theleading turn 274L. A second transition portion 292 defines a furtherdecreasing cross-sectional area of the tubular wall 254 leading into thetrailing turn 274T. The decrease in cross-sectional area serves toaccelerate the fluid stream, to segregate the finer particle to theouter wall for extraction at 262.

The flow splitter 272 of the illustrated inertial separator 250 moreparticularly includes a bifurcation 294 in the tubular wall 254, whichdivides the tubular wall 254 into the outlet portion 284 defining theseparator outlet 260, and branch conduit 296 defining an outlet passage298 forming the particle outlet 262. The outlet passage 298 is providedat the outside 278 of the through passage 256, such that particlesentrained in the fluid stream flowing along the outside of the throughpassage 256 are carried into the outlet passage 298. In anotherconfiguration, the branch conduit 296 can be eliminated, such that theparticle outlet 262 is formed as an opening or port in the outer side ofthe tubular wall 254.

FIGS. 16-17 are a top and a bottom view, respectively, of the inertialseparator 250 from FIG. 14. As noted above, the centerline 264 followsthe various turns and transitions of the inertial separator 250, and maybe substantially straight or linear at the inlet portion 282 and outletportion 284 of the tubular wall 254. The branch conduit 296 can define acenterline 300 which tangentially intersects the centerline 264 of theseparator outlet 260.

FIG. 18 is a schematic view of a section of the engine 10, showing theinertial separator 250 of FIG. 14-17 incorporated with the inducersection 106. As described above, the inducer section 106 can form aportion of the bypass conduit 82 of the bypass cooling circuit 76, andcan include at least one inducer 108. The separator outlet 260 of theinertial separator 250 can be located upstream of the inducer 108 andcan be in fluid communication with the inducer inlet 302, such that thefluid stream supplied to the inducer 108 is a reduced-particle stream.The inducer 108 accelerates and/or turns the reduced-particle stream andinjects the reduced-particle stream into the HP turbine 34. As describedabove, the inertial separator 250 can be configured to accelerate thereduced-particle stream as well. The concentrated-particle stream fromthe inertial separator 250 is not directed to the inducer 108 or turbine34, but rather is passed from the particle outlet 262 (not visible inFIG. 18, see FIG. 14) through the extraction vent 306.

FIG. 19 is a schematic view showing a modified version of an inertialseparator 250′ according to an eleventh embodiment, in which elements incommon with the inertial separator 250 of FIG. 14-17 are referred to bythe same reference numerals bearing a prime (′) symbol. The inertialseparator 250′ differs from the inertial separator 250 of FIG. 14 byincluding a flow splitter 272′ with multiple particle outlets 262′. Theparticle outlets 262′ are disposed along the outside 278′ of the throughpassage 256′, with multiple bifurcations 294′ and branch conduits 296′correspondingly provided.

The inertial separator 250′ can be used with the inducer section 106 asshown in FIG. 18. The particle outlets 262′ be in fluid communicationwith one or portion portions of the engine, such thatconcentrated-particle stream from the inertial separator 250′ to one ormore portions of the engine 10. For example, one particle outlet 262′can be in fluid communication with the LP turbine 36, another particleoutlet 262′ can be in fluid communication with the exhaust for theengine 10 under the fan casing 40, and yet another particle outlet 262′can be in fluid communication with another portion of the engine 10 tobe used for some auxiliary function 94, as indicated schematically inFIG. 3. The listing of possible places to direct theconcentrated-particle stream is not limiting. Other suitable places,such as into the high pressure rotor wheel space is a possible location.

Furthermore, a center portion of the tubular wall 254′ is illustrated indotted line to depict that there are numerous configurations for theparticle concentrator 270′. For example, the particle concentrator 270′can include varying combinations and configurations of turns andtransition portions, as described above. In another example, theinertial separator 250′ can include multiple separator inlets 258′and/or multiple separator outlets 260′, in addition to the multipleparticle outlets 262′ as shown.

FIG. 20 is a perspective view showing a centrifugal separator 310 forremoving particles from a fluid stream according to a twelfthembodiment. The centrifugal separator 310 includes a body 312 having awall 314 defining a through passage 316, with a separator inlet 318which receives a fluid stream, a separator outlet 320 through which areduced-particle stream is passed, and a particle outlet 322 throughwhich a concentrated-particle stream is passed. The through body 312generally defines a centerline 324 of the centrifugal separator, withthe centerline further generally defining an upstream direction 326 anddownstream direction 328 with respect to the centrifugal separator 310.

The centrifugal separator 310 further includes a particle concentrator330 and a flow splitter 332. The particle concentrator 330 of theillustrated embodiment includes an angular velocity increaser 334provided within the through passage 316, downstream of the separatorinlet 318, which is configured to impart an increased angular velocityto the incoming fluid stream.

In this embodiment, the body 312 can define an outer body, with the wall314 provided as an outer, annular wall. The outer, annular wall 314includes a leading cylindrical portion 336 defining the separator inlet318, which is tapered to trailing cylindrical portion 338 having asmaller diameter by frusto-conical portion 340, which necessarily neednot be a frusto-conical portion 340. Other shapes are possible, such asa constant radius portion.

The separator outlet 320 of the illustrated embodiment includes an exitconduit 342 fluidly coupled to the body 312, downstream of the angularvelocity increaser 334 and the flow splitter 332. The exit conduit 342is shaped to substantially preserve either the angular velocity relativeto the body centerline 324 or the tangential velocity relative to theengine centerline 12, including the speed and vector, of thereduced-particle stream as the reduced-particle stream is emittedthrough the separator outlet 320.

In the illustrated example, the exit conduit 342 includes at least oneturn which is configured to substantially follow the vector of thereduced-particle stream provided by the angular velocity increaser 334.The at least one turn can define a winding centerline 346 for the exitconduit 342. In the illustrated embodiment, the winding centerline 346follows a path which wraps at least partially around the centerline 324defined by the through passage 316. The exit conduit 342 can thereforedefine a winding passage 344 extending from the trailing cylindricalportion 338.

At the winding passage 344, the winding centerline 346 can followvarious forms of curves. For example, the winding centerline 346 canfollow a plane curve or a space curve. In another example, the radius ofthe winding passage 344, defined as the distance between the centerline324 and the winding centerline 346 can be constant or changing along theexit conduit 342, including increasing in the downstream direction. Inyet another example, the pitch of the winding passage 344, defined asthe angle between the centerline 324 and the winding centerline 346 at agiven point along the centerline 324, can be constant or changing alongthe exit conduit 342, including decreasing in the downstream direction.Some non-limiting examples of shapes for the winding passage 344 inwhich the winding centerline 346 follows a space curve includecorkscrew, helical and spiral. The space curve followed by the windingcenterline 346 can follow the streamline for a vector that substantiallypreserves either the angular velocity relative to the body centerline324 or the tangential velocity relative to the engine centerline 12 ofthe reduced-particle stream.

FIG. 21 is a cross-sectional view of the centrifugal separator 310 fromFIG. 20, taken along the centerline 324. A center body 348 can beprovided within the through passage 316, spaced from the annular wall314, and can extend axially along the centerline 324 of the centrifugalseparator 310.

In the illustrated embodiment, the center body 348 can extendcontinuously between the angular velocity increaser 334 and the flowsplitter 332. The center body 348 includes a first terminal end 350extending toward, and in some cases may extend beyond, the separatorinlet 318, and a second terminal end 352, which are joined by acylindrical core 354. The first terminal end 350 can be rounded, whilethe second terminal end 352 can extend to a closed end wall 356 of thecentrifugal separator 310. The angular velocity increaser 334 can bespaced from the end wall 356 to define a separation chamber 360therebetween forming a portion of the through passage 316 between thecore 354 and the annular wall 314.

The flow splitter 332 is fluidly downstream of the particle concentrator330, and splits the concentrated-particle stream from thereduced-particle stream. The flow splitter 332 of the illustratedembodiment includes an annular chamber 362 spaced radially outwardlyfrom the annular wall 314, which defines, at least in part, the particleoutlet 322. The particle outlet 322 further includes at least one outletpassage 364 having at least one inlet opening 366 and at least oneoutlet opening 368, with the inlet opening 366 extending radiallyinwardly from the annular wall 314.

As shown, the annular chamber 362 includes a leading wall 370 and atrailing wall 372 which project radially from the annular wall 314 andare joined by an outer wall 374. One annular outlet passage 364 isdefined by the annular chamber 362, with a circumferential inlet opening366 extending around the annular wall 314 and one outlet opening 368formed in the outer wall 374. The leading and trailing walls 370, 372define the inlet opening 366, which extends circumferentially around theannular wall 314. Alternatively multiple, separate inlet or outletopenings 366, 368 can be provided. Furthermore, one or more non-annularoutlet passages 364 can be provided.

The outlet passage 364 shown herein has an axially-increasingcross-section, such that the cross-section of outlet passage at theinlet opening is smaller than the cross-section of outlet passagedownstream of the inlet opening. In another configuration, the outletpassage can have an axially-constant cross-section or axially decreasingcross section.

FIG. 22 is a view similar to FIG. 21 showing the fluid flow through thecentrifugal separator 310 during operation. In operation, a fluid streamenters the separator inlet 318 in a substantially axial direction withrespect to the centerline 324, and the angular velocity increaser 334imparts a swirling flow to the incoming fluid stream, thereby generatinga vortex and/or a swirling flow within the separation chamber 360. Theangular velocity increaser 334 is configured to increase the angularvelocity of the fluid stream as the fluid stream passes through thethrough passage 316, thereby increasing the centrifugal force acting onentrained particles in the fluid stream to urge the entrained particlestoward the outer wall 314. The flow splitter 332 splits aradially-outward portion of the fluid stream along with entrainedparticles within the radially-outward portion from a radially-inwardportion of the fluid stream to form a concentrated-particle stream(illustrated by dotted line) and a reduced-particle stream. The exitconduit 342 receives the reduced-particle stream and substantiallypreserves either the angular velocity relative to the body centerline324 or the tangential velocity relative to the engine centerline 12,including the speed and vector, of the reduced-particle stream as thereduced-particle stream is emitted through the separator outlet 320. Theconcentrated-particle stream passes into the annular chamber 362 andthrough the particle outlet 322.

FIG. 23 is a schematic view of a section of the engine 10, showing thecentrifugal separator 310 of FIG. 20 incorporated with the inducersection 106, according to a thirteenth embodiment. As described above,the inducer section 106 can form a portion of the bypass conduit 82 ofthe bypass cooling circuit 76, and can include at least one inducer 108.The separator outlet 320 of the centrifugal separator 310 can be locatedupstream of the inducer 108 and can be in fluid communication with theinducer inlet 302, such that the fluid stream supplied to the inducer108 is a reduced-particle stream. The inducer 108 accelerates and/orturns the reduced-particle stream and injects the reduced-particlestream into the HP turbine 34. As described above, the centrifugalseparator 310 can be configured to accelerate the reduced-particlestream as well. The concentrated-particle stream from the centrifugalseparator 310 is not directed to the inducer 108 or turbine 34, butrather is passed from the particle outlet 322 through the extractionvent 306.

FIG. 24 is a perspective view showing one example of an inducer section376 that can be incorporated in the engine 10 according to a fourteenthembodiment. The inducer section 376 includes a ring-shaped body 378having a plurality of centrifugal separators 310 according to theembodiment of FIG. 20, and inducers 380, all of which may be integrallyformed or molded with the ring-shaped body 378. The ring-shaped body 378can be coaxially aligned on the centerline 12 of the engine 10 (see FIG.1).

FIG. 25 is a close-up view of a portion of the inducer section 376 ofFIG. 24, showing the fluid flow through the inducer section 376 duringoperation. The separator outlet 320 of the centrifugal separator 310 canbe located upstream of the inducer 380 and can be in fluid communicationwith an inlet of the inducer 380, such that the fluid stream supplied tothe inducer 380 is a reduced-particle stream. More specifically, asillustrated herein, a downstream portion of the exit conduit 342 canform a flow passage for the inducer 380, such that the exit conduit 342accelerates and turns the reduced-particle stream, and injects thereduced-particle stream into the HP turbine 34. An outlet for theinducer 380 can be defined by an opening 384 in a side face 386 of thering-shaped body 378 opposite the separator inlet 318.

FIGS. 26-32 show various optional modifications or additions to theengine 10 shown in FIG. 1, or bypass cooling circuit 76 shown in FIGS.2-3. Unless otherwise noted, it is understood that the followingoptional modifications or additions can further be combined with any ofthe embodiments of the particle separators discussed above.

FIG. 26 is a schematic view of a section of the engine 10, showing aportion of the bypass cooling circuit 76 incorporated with the HPturbine 34, according to a fifteenth embodiment. As described above,with reference to FIGS. 2-3, the bypass cooling circuit 76 can provide areduced-particle stream from the particle separator 86 to the HP turbine34 for cooling. In the illustrated embodiment, the concentrated-particlestream from the particle separator 86 is also utilized in the HP turbine34. As described above, the HP turbine 34 includes multiple stages 64,each stage 64 having at least one rotating blade 68 paired with at leastone static vane 72 (also called a nozzle). An inter-stage cavity 400 canbe defined between two of the turbine stages 64.

For at least one of the turbine stages 64 of the illustrated embodiment,the vane 72 has an exterior 402 and an at least partially-hollowinterior 404 which is in fluid communication with the separator outlet90 of the particle separator 86 in order to receive the reduced-particlestream from the particle separator 86 and cool the interior 404 of thevane 72. The vane 72 further includes a conduit 406 extending throughthe vane 72 which is fluidly isolated from the interior 404. The conduit406 is in fluid communication with the particle outlet 92 of theparticle separator 86 in order to receive the concentrated-particlestream from the particle separator 86. The conduit 406 can extend out ofthe vane 72 to supply the inter-stage cavity 400 with theconcentrated-particle stream in order to cool the exterior 402 of thevane 72. With the reduced-particle stream cooling the interior 404 andthe concentrated-particle stream cooling the exterior 402, vane coolingcan be increased while also minimizing the number of particles passed tothe interior 404 of the vane 72; using the concentrated-particle streamfor cooling the exterior 402 of the vane 72 is not as detrimental to theengine 10.

FIG. 27 is a schematic view of a section of the engine from FIG. 1showing a shroud assembly 408 according to a sixteenth embodiment. Theshroud assembly 408 is shown as being associated with the HP turbine 34,although the shroud assembly 408 can alternatively be associated withthe LP turbine. The shroud assembly 408 includes a shroud 410 whichsurrounds the blades 68 and a hanger 412 configured to couple the shroud410 with a casing of the engine 10. The shroud 410 includes a front side414 confronting one of the blades 68 of the HP turbine 34 and a backside 416 opposite the front side 414. The hanger 412 can directly mountthe shroud 410 to the core casing 46 of the engine (see FIG. 1), or canindirectly couple the shroud 410 with the core casing 46 via a hangersupport 418, as shown herein.

The shroud assembly 408 further includes a cooling conduit 420 extendingthrough at least a portion of the hanger 412 to supply a cooling fluidstream to the back side 416 of the shroud 410, and at least one particleseparator 422 forming part of the cooling conduit 420. For purposes ofsimplification, one particle separator 422 is shown in the coolingconduit 420 of FIG. 27, although it is understood that multiple particleseparators 422 may be present.

As illustrated, the cooling conduit 420 can enter the hanger 412 in anaxial direction with respect to the centerline of the engine 10.Alternatively, the cooling conduit 420 can enter the hanger 412 in aradial direction with respect to the centerline of the engine 10. Whenentering in a radial direction, the cooling conduit 420 may further passthrough a portion of the hanger 412 support.

The particle separator 422 includes a through passage 424 with aseparator inlet 426 which receives a fluid stream, a separator outlet428 through which a reduced-particle stream is passed, and a particleoutlet 430 through which a concentrated-particle stream is passed. Theparticle outlet 430 can be defined by a scavenge conduit 432 branchingfrom the through passage 424; in such a case, the concentrated-particlestream may form a scavenge flow stream.

The scavenge conduit 432 can have a scavenge outlet 434 that can befluidly coupled with a particle collector, an exhaust from the engine 10or with another portion of the engine 10 for utilization. In theillustrated embodiment, the scavenge outlet 434 is fluidly coupled withan inter-stage cavity of the HP turbine 34 and is located between thehanger 412 and the at least one vane 72 of the HP turbine 34. Thescavenge outlet 434 can be fluidly coupled downstream of at least oneblade 68 of the HP turbine 34 to provide the concentrated-particlestream to the exterior of the vanes 72 for cooling. The inlet of thescavenge conduit 432 is provided by the particle outlet 430 of theparticle separator 422.

In operation, as described above with reference to FIG. 2, the coolingfluid stream which enters the cooling conduit 420 can be provided fromthe source 80 of the bypass cooling circuit 76 or can be provided as areduced-particle stream from the particle separator 86 of the bypasscooling circuit 76. The cooling fluid stream enters the particleseparator 422 through the separator inlet 426 and the particle separator422 separates particles from the cooling fluid stream and forms aconcentrated-particle stream containing the separated particles, whichis directed along the scavenge conduit 432, and a reduced-particlestream, which is passed through the separator outlet 428 to the backside 416 of the shroud 410.

Using the illustrated shroud assembly 408, at least some of theparticles within the cooling fluid stream are removed before the coolingfluid stream reaches the back side 416 of the shroud 410. Withoutremoving particles, particles can accumulate on the back side 416 of theshroud 410 and can act as a thermal insulator that elevates the shroudtemperature. It is noted that some particles may remain in thereduced-particle fluid stream that reaches the back side 416 of theshroud 410. However, the remaining particles that are passed through theparticle separator 422 tend to be smaller, and so the overall amount ofparticles accumulated on the back side 416 of the shroud 410 is reduced,which in turn reduces the thermal insulation effect on the cooled sideof the shroud 410.

The particle separator 422 is shown only schematically in FIG. 27, butit is understood that the particle separator 422 may comprise any of thespecific embodiments shown herein. For example, the particle separator422 may be an inertial separator which separates particles from thecooling air flow using a combination of forces, such as centrifugal,gravitational, and inertial. More specifically, the inertial separatormay be the inertial separator 250 shown in FIGS. 14-17 or the inertialseparator 250′ shown in FIG. 19.

In another example, the particle separator 422 may be a centrifugal orcyclonic separator, which uses cyclonic action to separate particlesfrom the cooling air flow. More specifically, the centrifugal separatormay be the centrifugal separator 110 shown in FIGS. 4-9, the centrifugalseparator 110′ shown in FIG. 10, the centrifugal separator 110″ shown inFIG. 11, the centrifugal separator 210 shown in FIG. 12, or thecentrifugal separator 310 shown in FIGS. 20-22.

FIG. 28 is a schematic view showing a modified version of a shroudassembly 408′ according to a seventeenth embodiment, in which elementsin common with the shroud assembly 408 of FIG. 27 are referred to by thesame reference numerals bearing a prime (′) symbol. The shroud assembly408′ differs from the shroud assembly 408 of FIG. 27 by including aparticle separator in the form of an inertial separator 422′.

The inertial separator 422′ includes at least one turn 436 in thethrough passage 424′. The turn 436 defines an outer wall 438 of thethrough passage 424′, and the scavenge conduit 432′ branches from theouter wall outer wall 438. The at least turn 436 is shaped to change thedirection of the cooling fluid stream such that particles entrained inthe cooling fluid stream are carried by their inertia against the outerwall, where they enter the scavenge conduit 430′ along with a portion ofthe cooling fluid stream to form the concentrated-particle stream. Theat least one turn 436 can change the direction of the cooling fluidstream at least 90 degrees; more specifically, the at least one turn 436can change the direction of the cooling fluid stream at least 180degrees.

The separator inlet 426′ and separator outlet 428′ can be radiallyoffset from each other, relative to the centerline of the engine. Theseparator outlet 428′ can exit through a radially-inward portion of thehanger 412′ to supply the reduced-particle stream to the back side 416′of the shroud 410′. A baffle 440 having a plurality of openings 442 canbe positioned between the separator outlet 428′ and the back side 416′of the shroud 410′ to distribute the reduced-particle stream more evenlyover the back side 416′.

FIG. 29 is a schematic view showing a modified version of a shroudassembly 408″ according to an eighteenth embodiment, in which elementsin common with the shroud assembly 408 of FIG. 27 are referred to by thesame reference numerals bearing a double prime (″) symbol. The shroudassembly 408″ differs from the shroud assembly 408 of FIG. 27 byincluding a particle separator in the form of a centrifugal separator422″.

The centrifugal separator 422″ includes at least an angular velocityincreaser 444 located within the through passage 424″. An angularvelocity decreaser 446 can further be located within through passage,downstream of the angular velocity increaser 444. In such an embodiment,the scavenge conduit 432″ branch from the through passage 424″downstream of the angular velocity increaser 444 and upstream of theangular velocity decreaser 446.

FIG. 30 is a schematic view of a portion of the compressor section 22 ofthe engine 10 from FIG. 1, showing a baffle-type separator 448incorporated into the compressor section 22 according to a nineteenthembodiment. In this embodiment, the baffle-type separator 448 forms aportion of the bypass cooling circuit 76 upstream of the hot portion ofthe engine 10 to which the cooling fluid is to be provided. Thebaffle-type separator 448 includes a baffle 450 (such as a scoop orlouver) integrated into the cooling conduit 78. The baffle 450 isconfigured to force the fluid stream to turn, which has the effect ofseparating at least some of the particles out of the fluid streaminstead of passing the particles downstream.

The baffle 450 can be positioned within a plenum 452 defining a throughpassage 454 and having a separator inlet 456 in fluid communication withone of the compressor stages 52, 54 of the compressor section 22 toreceive a fluid stream, a separator outlet 458 through which areduced-particle stream is passed, and a particle collector 460 in whichseparated particles are collected. The separator outlet 458 can be influid communication with a hot portion of the engine for cooling, suchas the hot portion 78 shown in FIGS. 2-3, or with a downstream particleseparator, such as the particle separator 86 shown in FIGS. 2-3 forfurther separation. The particle collector 460 can be configured to beaccessed for service, such as for emptying the particle collector 460.

When entering the separator inlet 456 from the compressor stage 52, 54,the fluids stream may be swirling circumferentially and moving axially.The baffle 450 is oriented in the plenum 452 between the separator inlet456 and separator outlet 458, for example in opposition to the separatorinlet 456, to define a bend 462 in the through passage 454 directed awayfrom the direction of the fluid flow, such that fluid must make a turnaround the baffle 450 in order to reach the separator outlet 458. Asshown herein, the baffle 450 may be provided as a plate 464 extending inthe aft direction at an angle toward the centerline 12 of the engine 10.The plate 464 may define a substantially 180° bend 462 for the fluidstream.

FIG. 30 shows an upper portion of the compressor section 22 above thecenterline 12 of the engine 10, and for this portion the particlecollector 460 is provided as a radially-inward pocket 466 in an aft wall468 of the plenum 452. It is noted that for the lower portion of thecompressor section 22 below the centerline 12 of the engine 10, theparticle collector 460 is provided as a radially-outward pocket 470 inthe aft wall 468.

It is noted that both the baffle 450 and the plenum 452 can extendannularly about the centerline 12 of the engine, and further thatmultiple separator inlets 456, separator outlets 458, and/or particlecollectors 460 can be spaced circumferentially about the centerline 12.

In operation, the fluid stream entering the separator inlet 456 willmake a turn around the baffle 450 to reach the separator outlet 458. Dueto inertial forces, at least some, if not a majority of, the particlesentrained within the fluid stream will not make the turn, and willinstead strike the aft wall 468 of the plenum 452 and fall into theparticle collector 460. The fluid stream which turns around the baffle450 will therefore have a lowered concentration of particles, therebydefining a reduced-particle stream. The reduced-particle stream thenexits through the separator outlet 458.

FIG. 31 is a schematic view showing a modified version of a baffle-typeseparator 448′ according to a twentieth embodiment, in which elements incommon with the baffle-type separator 448 of FIG. 30 are referred to bythe same reference numerals bearing a prime (′) symbol. The baffle-typeseparator 448′ differs from the baffle-type separator 448 of FIG. 30 byincluding multiple baffles 450′ within the plenum 452′. As shown herein,the baffles 450′ are provided as plates 464′ substantially aligned witheach other and extending in the aft direction at an angle toward thecenterline 12 of the engine 10. The plates 464′ are spaced from eachother to define multiple bends 462′ for the fluid stream.

FIG. 32 is a schematic view showing a modified version of a baffle-typeseparator 448″ according to a twenty-first embodiment, in which elementsin common with the baffle-type separator 448 of FIG. 30 are referred toby the same reference numerals bearing a double prime (″) symbol. Thebaffle-type separator 448″ differs from the baffle-type separator 448 ofFIG. 30 by including multiple baffles 450″ within the plenum 452″, aswell as by being configured to create a concentrated-particle streamwhich contains the separated particles, rather than collecting theseparated particles in a particle collector.

As shown herein, the baffles 450″ are provided as substantiallyradially-oriented plates 464′ with respect to the centerline 12 of theengine 10. The plates 464″ are substantially aligned with each other andare spaced from each other to define multiple bends 462″ for the fluidstream.

The through passage 454″ further includes a particle outlet 472 throughwhich the concentrated-particle stream is passed. The particle outlet472 can be defined by a wall 474 extending radially with respect to theseparator inlet 456″ that is spaced from an upstream side of the baffles450″ as well as from a radially-outward wall 476 of the plenum 452″ todefine an outlet passage 478 branching from the through passage 454″.Via the outlet passage 478, the concentrated-particle stream canoptionally be returned to the compressor section 22 via a conduit 480leading to an inter-stage cavity, or can be exhausted from the engine 10via a conduit 482 leading to a bleed cavity.

The various embodiments of systems, methods, and other devices relatedto the invention disclosed herein provide improved particle separation,particularly in a turbine engine. One advantage that may be realized inthe practice of some embodiments of the described systems is that thevarious embodiments of systems, methods, and other devices disclosedherein may be used, alone or in combination, to remove particles from acooling air flow in a turbine engine. The reduction of particles in thecooling air can improve cooling and engine component durability. Anotheradvantage that may be realized in the practice of some embodiments ofthe described systems and methods is that both the reduced-particlestream and the concentrated-particle steam created by the particleseparation may be utilized within the engine.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A turbine engine comprising: a fan providing anambient air stream through the turbine engine; a compressor sectionwhich receives the ambient air stream and emits a compressed stream; acombustion section which receives the compressed stream and emits acombustion stream which is at a higher temperature than the compressedstream; a turbine section which receives the combustion stream and emitsan exhaust stream which is at a lower temperature than the combustionstream; a rotatable drive shaft coupling a portion of turbine sectionwith a portion of the compression section and defining a rotational axisfor the turbine engine; a bypass fluid conduit coupling either the fanor the compressor section to the turbine section while bypassing atleast the combustion section to supply either a portion of the ambientair stream or a portion of the compressed stream, respectively, to theturbine section to define a bypass stream, without providing work on thebypass stream that would increase the pressure or decrease thetemperature of the bypass stream; and at least one particle separatorfixedly located in the turbine engine for non-rotation relative to therotational axis and further located within the bypass fluid conduit toseparate particles from the bypass stream prior to the bypass streamreaching the turbine section to form a reduced-particle stream that isprovided to the turbine section for cooling.
 2. The turbine engineaccording to claim 1, wherein the particle separator further comprises:a particle concentrator located within the bypass fluid conduit andconcentrating at least some of the particles entrained in the bypassstream from one portion of the bypass stream into another portion of thebypass stream to functionally provide the bypass stream with aconcentrated-particle stream and the reduced-particle stream; and a flowsplitter having a particle outlet downstream of the particleconcentrator and located to receive at least a portion of theconcentrated-particle stream to split the at least a portion of theconcentrated-particle stream from the reduced-particle stream.
 3. Theturbine engine according to claim 2, wherein the particle concentratorcomprises an angular velocity increaser.
 4. The turbine engine accordingto claim 3, wherein the angular velocity increaser comprises at leastone vane located within the bypass fluid conduit and shaped or orientedto increase the angular velocity of the bypass stream.
 5. The turbineengine according to claim 4, wherein the at least one vane comprises atleast one helical vane or a plurality of radially spaced vanes.
 6. Theturbine engine according to claim 2, wherein the particle concentratorcomprises a turn in the bypass fluid conduit.
 7. The turbine engineaccording to claim 6, wherein the turn effects at least a 45 degreechange of direction of the bypass stream.
 8. The turbine engineaccording to claim 6, wherein the turn comprises a continuous portion,or a winding portion, of the bypass fluid conduit.
 9. The turbine engineaccording to claim 1 and further comprising an inducer having an inducerinlet fluidly coupled with the at least one particle separator toreceive the reduced-particle stream and an inducer outlet supplying thereduced-particle stream to the turbine section.
 10. The turbine engineaccording to claim 1, wherein the at least one particle separatorcomprises a separation chamber having: a separator inlet receiving thebypass stream; a separator outlet fluidly coupled with the turbinesection and receiving the reduced-particle stream; and a particle outletreceiving a concentrated-particle stream comprising the separatedparticles.
 11. The turbine engine according to claim 10, wherein theturbine section comprises at least one vane with an interior and aconduit isolated from the interior, wherein the conduit is in fluidcommunication with the particle outlet for receiving theconcentrated-particle stream from the at least one particle separator.12. The turbine engine according to claim 11, wherein the interior ofthe at least one vane is in fluid communication with the separatoroutlet for cooling by the reduced-particle stream from the at least oneparticle separator.
 13. The turbine engine according to claim 11,wherein the turbine section comprises at least two turbine stages, withan inter-stage cavity between the at least two turbine stages, andwherein the conduit is in fluid communication with the inter-stagecavity to supply the concentrated-particle stream to the inter-stagecavity.
 14. The turbine engine according to claim 1, wherein the bypassfluid conduit comprises at least one baffle configured to force thebypass stream to turn to separate particles from the bypass stream priorto the bypass stream reaching the at least one particle separator. 15.The turbine engine according to claim 14, wherein the bypass fluidconduit is fluidly coupled to the compressor section, and the compressorsection comprises at least one particle collector configured to collectthe particles separated by the at least one baffle.
 16. The turbineengine according to claim 14, wherein the at least one baffle defines asubstantially 180° turn for the bypass stream, or comprises multiplebaffles.
 17. A centrifugal separator for removing particles from a fluidstream, comprising: a body having a wall defining a through passage,with a separator inlet and a separator outlet; an angular velocityincreaser located within the through passage downstream of the separatorinlet and configured to increase the angular velocity of a fluid streamentering the separator inlet as the fluid stream passes through thethrough passage; a particle outlet configured to receive aconcentrated-particle stream containing particles urged toward the wall;an angular velocity decreaser located within the through passage,downstream of the angular velocity increaser and upstream of theseparator outlet, and configured to decrease the angular velocity of areduced-particle stream prior to passing through the separator outlet;and a bend provided in the body between the angular velocity increaserand the angular velocity decreaser.
 18. The centrifugal separator ofclaim 17, wherein the angular velocity increaser and the angularvelocity decreaser respectively increase and decrease the angularvelocity of the fluid stream by substantially opposite amounts.
 19. Thecentrifugal separator of claim 17, wherein at least one of the angularvelocity increaser and the angular velocity decreaser comprises aplurality of stationary vanes.
 20. The centrifugal separator of claim19, wherein the plurality of stationary vanes are circumferentiallyspaced relative to a centerline of the through passage.
 21. Thecentrifugal separator of claim 17, wherein the particle outlet comprisesan outlet passage having an inlet opening adjacent the wall, wherein theangular velocity decreaser is located downstream of the outlet passage.22. The centrifugal separator of claim 21, wherein the wall defines adiameter D, and the inlet opening is located 1-20 D downstream from theangular velocity increaser.
 23. The centrifugal separator of claim 22,wherein the outlet passage extends radially inwardly into the throughpassage between 1%-20% of the diameter D in a downstream direction. 24.The centrifugal separator of claim 22, wherein the inlet opening definesa radial segment R of 1%-10% of the diameter D.
 25. The centrifugalseparator of claim 21, wherein the outlet passage comprises anaxially-increasing cross section.
 26. The centrifugal separator of claim21, wherein the wall comprises a outer annular wall, and the outletpassage comprises an inner annular wall spaced radially inwardly fromthe outer annular wall to define the inlet opening, wherein the innerannular wall extends the full circumference of the outer annular wall.27. The centrifugal separator of claim 26, wherein the inner annularwall defines the separator outlet.
 28. The centrifugal separator ofclaim 26, wherein the outlet passage further comprises an outlet openingformed in the outer annular wall.
 29. The centrifugal separator of claim17, wherein at least a portion of the particle outlet lies upstream ofthe angular velocity decreaser.
 30. The centrifugal separator of claim17, wherein: the angular velocity increaser comprises a first set ofvanes located within the through passage and oriented relative to thefluid stream to increase the angular velocity of the fluid stream as thefluid stream passes through the first set of vanes; the angular velocitydecreaser comprises a second set of vanes located within the throughpassage and oriented relative to the fluid stream to decrease theangular velocity of the reduced-particle stream as the reduced-particlestream passes through the second set of vanes; the particle outlet isdefined by a passage extending along an inner periphery of the wall,with the passage defining an opening; and the opening is upstream of thesecond set of vanes.
 31. The centrifugal separator of claim 30, wherein:the passage extends along the entire inner periphery of the wall; andthe passage comprises an axially-increasing cross section.
 32. Thecentrifugal separator of claim 17, and further comprising a center bodywithin the through passage and extending along a centerline of thethrough passage.
 33. The centrifugal separator of claim 32, wherein thewall comprises an annular wall defining the through passage, and thecenter body extends through the through passage spaced from the annularwall.
 34. The centrifugal separator of claim 32, wherein the angularvelocity increaser comprises a first set of vanes located on a first endof the center body and the angular velocity decreaser comprises a secondset of vanes located on a second end of the center body.
 35. Thecentrifugal separator of claim 17, and further comprising a leadingcenter body adjacent the separator inlet and a trailing center bodyadjacent the separator outlet and separate from the leading center body,wherein the leading center body and the trailing center body extendalong a centerline of the through passage.
 36. The centrifugal separatorof claim 35, wherein the angular velocity increaser comprises a firstset of vanes located on the leading center body and the angular velocitydecreaser comprises a second set of vanes located on the trailing centerbody.
 37. The centrifugal separator of claim 17, wherein the bend is atleast 45 degrees.
 38. The centrifugal separator of claim 37, wherein thebend is less than or equal to 90 degrees.